1. Field of the Invention
The present invention relates to a testing apparatus for testing of electronic devices, and to a power supply circuit for use in such a testing apparatus or other like apparatus.
2. Description of Related Art
Conventionally, a testing apparatus which performs tests on electronic devices is provided with a power supply circuit for powering the testing apparatus. For example, the power supply circuit has a power device configured to generate a power supply voltage and a power supply current for supply to an electronic device, and a power supply for driving the power device.
For example, the power device has an amplification circuit for amplifying an applied input voltage and producing an output as a power supply voltage, a source-side circuit for supplying a source current to the electronic device according to the input voltage, and a sink-side circuit for drawing a sink current from the electric device according to the input voltage. Each of the source-side circuit and the sink-side circuit has a CMOS disposed between the power supply and the electronic device. A voltage according to the input voltage is supplied to a gate terminal of each of the CMOSs, and whether the power supply current is to be supplied to the electronic device from the power supply or it is drawn to the power supply from the electronic device, is controlled according to the input voltage.
In a conventional power supply circuit, however, the drive voltage, which is applied to the power device from the power supply, is constant. Besides, a differential between the drive voltage and the power supply voltage is supplied to the source-side. For example, when, at this time, the power supply voltage becomes extremely low, this causes application of a voltage of approximately the same level as the drive voltage to the source-side circuit and the sink-side circuit, with the result that the consumption of power in the power device increases.
Accordingly, an object of the present invention is to provide a testing apparatus and a power supply circuit which can solve the problems discussed above. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.